Hydraulic powered flying controls



Feb. 7, 1961 JJJJJJJJ HA M 2,970,443

HYDRAULIC PO ER CONTROLS Feb. 7, 1961 J. SPRINGHAM 2,970,443

HYDRAULIC POWERED FLYING CONTROLS Filed Nov. 19, 1958 2 Sheets-Sheet 2 INVENTOR J/l/V SP/NG-/IAM by MM M im ''TORNEYS.

United S ates P tn QO HYDRAULIC POWERED FLYING CONTROLS John Springham, Brough, England, assignor to Blackburn and General Aircraft Limited, Brough, England, a British company Filed Nov. 19, 1958, Ser. No. 775,068

Claims priority, application Great Britain Dec. 16, 1957 4 Claims. (Cl. GO-97) This invention relates to improvements in hydraulic powered flying Controls, and has for its object to provide sucha control system which is simple' yet reliable, which will fail safe, and which is without electrical, mechanical or hydraulic operated cut-out or change-over devices subject to fail and decrease the overall reliability of the control system.

To this end according to the present invention, a control surface is moved by three mechancally-paralleled but otherwise independent servo-Controlled piston jacks with resilient means interposed between movement applying members and servo-valve actuating members. Each jack has a non-return valve in a duct between oppo site ends of its cylinder. V

Further according to the present invention each of the three jacks is in a separate hydraulic circuit, pressurised from a common or separate source of power., Thus each circuit may be operated by one engineoi a 'multi-' engine aircraft or two by the aireraft engines' and the third by a separate powerplant. 3

- Still further according to the' present' invention the movement applying means may be duplicated and connected to a mechanical part the movement of which is taken to the three servo-valve actating'members.

In normal use the three jacks will actsimultaneously with 'equal effect to move the control surface. Should a servo-valve jam, full movement of the'mechanism can still take place due to the action of the resilient means,

conveniently in the form of a spring box, of the jammed valve, as the non-return valve of the jack with the jammed servo-valve will allow movementof that jack. A switch may be provided to give an indication of (a jammed valve. With one valve not Operating, the'other two give /3 power which is adequate to move the control surface. v g

A hydraulic failure in any one of the three circuits, due to a burst or power failure, again only loses the power of one jack. In an extreme case of failure of two jacks, either due to jammed'valves and/ or hydraulic failure, the remaining valve giving /3 power available will still operate and give sufiicient stitiness to avoid flutter of' the control surface.

If a power plant independent of the aircraft engines,

The triple jack actuator herenafter described is preferably operated by duplicated Controls, such as are already known'in the art, in which two movement imparting rods A, A (see Fig. 1) normally move together but a failure in one half of the control system allows one such rod to move to impart the pilot's movements to the servo-valves without being mpeded by the other rod. I Each of the Operating rods A, A is connected to a three arm pivoted member C forming a mechanical paralleling device and pivoting with respect to the bodies or common body B of three jacks of the double acting differential area typeyeach Controlled by a servo-valve E'. The bodies of the three jacks are connected together and to the actuating member L of the aircraft control surface. The rams M of these jacks are connected to the aircraft structure.

The movement of the member C is taken to the respective servo-valves E by rods Sl, S2, each of which rods has an end disposed in telescoping fashion in a springbox D, whose spring is pre-loaded in excess of the maximum valve Operating load so that with any valve jammed there may be full movement of the rods Sl, S2 of the other valves.

As may be seen in Fig. 2, each jack is of the diiferential area type having chambers I-I and J separated by the jack piston T and fed with the full hydraulic system pressure applied from the' inlet P to the Chamber H through the port W and duct .F, and applied to the Chamber J through port K and duct G. The area of side J' of the piston T to which pressure s applied in' Chamber J is approximately twice the anuular 'area of side'H' to which pressure is applied in Chamber H. Thejack 'exhausts 'through the outlet R providing a return:

to tank connection means for hydraulic fluid.- As illustrated the piston T of the ja'ck is in Substantially mid-'position and the servo valve E is in neutral position in which there is no flow of hydraulic fluid. On dsplacement of the rods Sl, S2 to the left, the servovalve E uncovers port K putting the jack Chamber J in communication with the Outlet R via duct G resulting in dsplacement of jack body B to the left.

On dsplacement of the rods Sl, S2 to the right, servo valve E uncovers 'port K putting jack Chamber J in communication with the pressure inlet connection P via duct G. Both chambers H and J are under common pressure and'due to the diflerential area of oppostesides of piston T, dsplacement of jack body B to the right will ensue.

Since rams M are attached to the aircraft and since jack body B is attached to actuating'member L of the aircraft control surface, movement of the jack body to v the right or left (in Fig. 2), as explainedabove, Causes supplies' power to the hydraulic circuit of one jack or can supply power to all three circuits, the-effect' of air- Craft engine failure is avoided and enables ground testing to be carried out without the engines running. The three jacks may be in a common housing or each jack may be separate and identical for convenient cons nection and replacement.

. An embodiment of a triple jack, mechancally-parallel .aetuator is by way of example hereinafter more fully de scribed with reference to the dr'awings, in which:*

. Fig. 1 is a perspective view of the three jacks with a corresponding movement of the aircraft control surface L. A. non-return 'valve NR is introduced between jack Chamber J and inlet connection P to prevent a hydraulic lock oecurring in the event .of the servo-valve E becoming jammed in the neutral position.

' The jacks are of ditferential area type as' stated above. The ;piston rod or ram M reduces the efir'ective area of the piston in Chamber H. If equal pressure is applied to both sides of the piston on movement of valve E to the right .from the position shown in Fg. 2,' a greater force will be applied' to the larger area side J' and body B of the jacks will move to the right from the position shown inFig. 2 since rod M is fixedly connected to the aircraft E to the left from the position shown in Fig.. 2, the body B of the jacks moves towards the left from theposition' shown in Fig. 2.' The aircraft control surface which isrconnected to 'body Bmoves in-accordance with move ments or' body B with respect to the air-Craft structure which the rods M are connected.

The valve can jam under ;any of three conditions, with:

(l) The port ;K closed (as shown in Fig. 2); (2) The .port K ,connected to pressure port P, .or (3) The port K connected to return or exhaust port R.

In case 1 with a servo-valve jammed with the port K closed (as shown in Fg. 2)

(a) On selection of extension of the jacks (body B moving to the right) the lever C is rocked to the right. The spring in box D of the jammed servo-valve is compressed which allows normal travel of the other two servo valves E to the right to connect their ports K to the ressure ports P of their respective jack bodies.

V Pressure is now supplied to three compartments H and two compartments J; the jack body with the jammed servo-valve having no pressure supply to compartment J as port K is closed due to the jammed servo-valve. Now since the area J' is at least twice the area of H', the tendency to Contract 'the three jacks is equal to three times the area of H' whereas the tendency to extend the jacks is equal to .two times the area of J J' is at least two times the area of H', two times the area of J' is equivalent to four times the area of H'. Therefore the net force tending to extend the jacks is equal to the pressure times one-half times the area of J'.

(b) 'On selection of contraction of the jacks (body B moving to the left), the lever C (Pig. 2) is rocked to the left and the spring in box D of the jammed servevalve allows normal travel of the remaining two servovalves E to the left which connects their ports K to the return or exhaust ports R. Pressure is now supplied to three compartments H and two compartments J are connected 'to the return or exhaust ports R, the jack body with the jammed servo-valve having no outlet from compartment I to ,exhaust as its port K is closed due to the jammed serve-valve,

The tendency to ,Contract the jacks is now equal to three times jthe'area I- I', and is resisted by the area J' of the body having the jammed servo-valve.

(1) As mentioned above .the area of J is equal to two times .the area of I'l', Two times the area ofl-I' will be required to balance the area o J' of the body having h iam d s r a ng .a ,n t f c appli d qmp rtm n .Hem l r/ O e t m s. t r a of H' to produce 'o c on' f he acks- Th Pr ss r bu ldp (i om m n J of he y B having the jammed servo-valve is relieved through a non-return valve NR (Fig. 2) into the pressure line, thereby'preventing a hydraulic locked condition.

(2) In case 2 with one servo-valve jammed and with the port K connected to pressure port P (a) On selecting extension of the jacks (body B moving to the right) lever C (Fig. 2) is rocked to the right and the spring in box D, of the jammed servo-valve is compressed, thus allowng normal travel of the other two servo-valves E to the right which connects the ports K to the pressure ports P of their respective jacks.

Pressure is now supplied to three compartments J and the triplicated jack unit extends in a .normal manner under full load.

(b) On selecting eontraetion of the jacks (body B moving to the l ft) the lever C (Fig. 2) is moved to the left. The spring in box D of the jammed servo-valve will be compressed and allow normal travel of the remaining two servo-valves to the left which connects the ports K-to the return or exhaust port R of their respective jacks.

Pressure is now supplied to three compartments Hand simultaneously pressure is supplied to One compartment J of the jammed servo-valve.

As previously mentioned One area J' is equal to twon are s FGQSQ there ema ns e One area H' On Since the area of r the tripli- (3) 'In case 3 with One port K connected to return 'or exhaust port R (a) On selecting extension of jacks (bodies moving to the-right) the 'lever C (Pig. .2) is rocked to the right, the

spring in box D of .the jammed servo-valve is compressed and allows normal travel of the other two servo-valves E to the right which connects the ports K to the pressure ports P .of their .respective jacks.

' Pressure is now supplied to three compartments H and simultaneously to two compartments J whilst ,compartment J of the jammed servo-valve body is connected 'to return or exhaust. The area available for extension is two times the area J' and is opposed by the area of three times 'H'. Thus the pressure times one-half the area of one J' s available for extension.

(b) On selecting contraction of the jack (bodies moving to the left) the lever C (Fig. 2) is rocked to the left. The spring in box D of the jammed servo-valve may be compressed (depending on position of jamming) allowing normal travel of the other two servo-valves, to the left which connects the ports K to the return or exhaust ports R of their respective jack bodies.

Pressure is now supplied to three compartments H 'and the three ,compartments J are connected to return or e aust.

, T e' ,triplicated jacks unit contracts norrnally under full load 'i.e., pressure times the area of three piston faces H'. In the event of a jammed servo-valve where its port K is connected to the return or exhaust port R, .there is available for extension of the triplicated jack .unit :the

pressure times one-half of the area of one piston side J', and on contracton the unit functions normally.

, A feature of this device is that under all circumstances there is eontinuous control, there being no time lag in pe a ion.

failure rendering the three jacks inoperative. rate hydraulic circuits may be pressurised by separate engines of a multi-engine aircraft.

' With this assurance and duplication of the plot's Controls, as already mentioned, a complete break-downis most unlikely and in all but an extreme case One operat ing rod A or A Will actuate the servo valve of at least one of the three jacks to effect movement of the aircraftt control surface.

'The triple jack actuators may operate the tail planes, rudder, and ailerons of the aircraft when the triplicated hydraulic circuits are paralleled or branched to the sets of three jacks controlling pairs of control surfaces.

claim:

' 1. In a hydraulic powered flying control system, three parallel differential pressure type piston jacks, each jack comprising a ram and a body, means supplying pressursed hydraulic fluid to said jacks, a servo Valve for each. of said jacks for controlling the supply of fluid, each of' said jack bodies including a cylinder with a piston theren movable by a ram, said piston dividing the cylinder into two chambers, each body having a duct Opening into said chambersj at opposite ends of the cylinder, a non-return valve displosed in the duct, inlet and outlet ports in the body ,communicating with said duct at opposite sidesofthe non-return valve, said servo-valve being located -in a path of said fiuid between said ports and said duct, a

mechanical part for simultaneously actuating said servo. valves, a control member, means connectlng said con- 2. In a hydraulc powered flying control system, three parallel difierential pressure type piston jacks, each jack comprising a ram and a body, a separate hydraulic system supplying pressurised fluid to each of said jacks, a servo valve controlling the supply of fluid to each jack, each of said jack bodies including a cylinder with a piston therein movable by a ram, said piston dividing the cylin der into two chambers, each body having a duet opening into said chambers at opposite ends of the cylinder, a non-return valve disposed in the duct, inlet and outlet ports in the body communicating with said duet at opposite sides of the non-return valve, said servo-valve being located in a path of said fluid between said ports and said duct, an Operating member including a resilient device for actuating each servo valve, a mechanical part, means for connecting said Operating members to said mechanical part, duplicated control members, means connecting said control members to said .mechanical part, a control surface Operating member, and means for imparting the movement of said jacks to said Operating member.

3. In a hydraulic powered flying control system, three difierential area pressure type piston jacks connected in parallel, each jack comprising a ram and a body, means connecting the rams of said jacks to fixed structure, means connecting the bodies of said jacks to a member moving a control surface, a servo valve controlling the supply of pressurised hydraulic fluid to each of said jacks, 'each of said jack bodies including a cylinder with a piston therein movable by a ram, said piston dividing the cylinder into two chambers, each body having a duet opening into said chambers at opposite ends of the cylinder, a nonreturn valve disposed in the duct, inlet and Outlet ports in the body communcating with said duet at opposite sides of the non-return valve, said servo-valve being located in a path of said fluid between said ports and dilferental area pressure type piston type jacks each comprising a ram and a body, means connecting said jack bodies in parallel, means connecting said jack bodies to a member moving a control surface, a separate supply of pressurised hydraulic fluid to each of said jacks, a servo valve for controlling the supply of said fluid to each of said jacks, each of said jack bodies including a cylinder with a piston therein movable by a ram, said piston dividing the cylinder into two chambers, each body having a duct opening into said chambers at opposite ends of the cylinder, a non-return valve disposed in the duct, inlet and Outlet ports in the body communicating with said duet at opposite sides of the non-return valve, said servo-valve being located in a path of said fluid between said ports and said duct, a servo valve actuating member including a resilient device, a three limb member pivoted to said jack bodies, means connecting saidservo valve actuating members each to a limb of said three limb member, independently operable duplicate control means, and means for connecting said control means to said three limb member.

References Cited in the file of this patent UNITED 'STATES PATENTS Lisle Mar. 25, 1952 2,597,4l8 Westbury et al. May 20, 1952 2,S97,419 Westbury et al. May 20, 1952 

